1. Field of the Invention
The present invention relates to a lithography apparatus and a focusing method for a charged particle beam, for example, a variable-shaped electron beam lithography apparatus using first and second aperture plate members and a focusing method for the electron beam.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor manufacturing processes. In recent years, with an increase in integration density of an LSI, a circuit line width required for a semiconductor device is getting smaller year by year. In order to form a desired circuit pattern on such a semiconductor device, a high-precision original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam lithography technique essentially has an excellent resolution, and is used in production of high-precision original patterns.
FIG. 9 is a conceptual diagram for explaining an operation of a variable-shaped electron beam lithography apparatus.
The variable-shaped electron beam (EB: Electron Beam) lithography apparatus operates as described below. In a first aperture plate 410, a quadrangular, for example, rectangular opening 411 to shape an electron beam 330 is formed. In a second aperture plate 420, a variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 of the first aperture plate 410 into a desired quadrangular shape is formed. The electron beam 330 irradiated from the charged particle source 430 and having passed through the opening 411 of the first aperture plate 410 is deflected by a deflector, passes through a part of the variable-shaped opening 421 of the second aperture plate 420, and is irradiated on a sample 340 placed on a stage continuously moving in one predetermined direction (for example, X direction). More specifically, a quadrangular shape which can pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 is lithographed in a lithography region on the sample 340 placed on the stage continuously moving in the X direction (for example, see Published Unexamined Japanese Patent Application No. 2007-043083). The scheme for causing a beam to pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 to form an arbitrary shape is called a variable-shaping scheme.
In the variable-shaped electron beam lithography apparatus, as described above, abeam is caused to pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 to shape the beam to be lithographed. For this reason, in order to perform high-precision shaping, a first aperture image is required to be focused on the second aperture plate. However, as a focusing method between the first and second aperture plates in an imaging system, a method of performing focusing with sufficient precision is not established.
As described above, a method of performing focusing with sufficient precision between the first and second aperture plates is not established.